1. Field of the Invention
The present invention relates to a magnetooptic device, a magnetooptic head, and a magnetic disk drive each performing optically assisted magnetic (OAM) recording in which information is recorded onto a magnetic recording film or a magnetooptic recording film by using a beam spot and a magnetic field and information is reproduced by using a magnetic gap or a magnetic sensor.
2. Description of the Prior Art
In a hard disk drive for recording and reproducing information by using a magnetic recording film, a magnetoresistive (MR) sensor using a magnetoresistive effect and a high-sensitive high-resolution GMR (giant-magnetoresistive) sensor (hereinbelow, the sensors will be collectively called MR sensors) have been developed for reproduction, and the recording density has been increased at an annual rate of 60 percent in the past several years. It has been however found recently that the limit of surface density is about 30 Gbits/inch2 due to the super paramagnetic effect, that is, an effect that the direction of the magnetization in a certain magnetic domain is reversed by the adjacent magnetization in the opposite direction due to thermal fluctuation (R. L. White, Tech. Digest of MORIS, '99, 11-A-03, (1999), p. 7).
As a promising method for solving the problem, OAM (Optically Assisted Magnetic) recording has been proposed. According to the method, a magnetization film is heated by irradiation of a laser beam to lower the intensity of magnetization of the film and, in such a state, information is recorded. By this method, information can be recorded onto a magnetic film having a high coercive force and the reversal of magnetization at the room temperature is prevented.
An example of such a conventional magnetooptic head is described in Nikkei Electronics No. 734, Jan. 11, 1999, p. 35.
FIG. 20 shows the magnetooptic head. In the magnetooptic head 100, a beam spot 107 is formed on a light-receiving surface 106b of an SIL 106 by a condensing lens 105, and a coil 110 is provided around the light-receiving surface 106b. While modulating a magnetic field by the coil 110 on the basis of an information signal for recording, a magnetooptic recording film 51a on an optical disk 51 is intermittently irradiated with a near field wave 107a leaked from the light-receiving surface 106b to thereby record information (this will be called laser-pumped modified field magnetic (LP-MFM) recording, thereby enabling a recording mark having a length shorter than the diameter of the beam spot to be formed). Information is reproduced by using a magnetic sensor 111 using a magnetoresistive thin film as a sensing portion. According to the method, the size of the condensed beam spot 107 can be reduced in inverse proportion to the refractive index of the SIL 106, so that a small recording magnetic domain having a width of about 0.3 μm can be formed and high recording density can be implemented.
According to the conventional magnetooptic head, however, the coil for generating the modulated magnetic field and the magnetic sensor for reading magnetic information are provided separate from the semiconductor laser and the optical system. Due to the arrangement, the magnetooptic head has problems such that its size is large and the transfer rate cannot be increased due to the limitation in reducing the weight.